The present invention relates generally to, signal processing and is more particularly directed to a sigma-delta modulator for use in voiceband, audioband, or higher-frequency signal processing.
Sigma-delta signal processing techniques are useful for data encoding in modem and other higher-frequency applications where they promise high-resolution and high-linearity data conversion. In addition to high resolution and high linearity, they are desirable in part because they are readily implemented with MOS integrated circuit technology. Other important advantages are that a sigma-delta system consists largely of digital circuity and can therefore be scaled efficiently in area as MOS feature sizes shrink and that the analog components used are more tolerant of component mismatches normally associated with digital MOS technologies.
However, as the signal bandwidth to be processed increases, greater demand is placed on the performance of the components to the point where impairments in the analog components become significant in preventing the sigma-delta processor from achieving its theoretical performance limit.
In known sigma-delta systems a balance must be struck between sampling the desired signal at a slower rate, resulting in either limited frequency range of operation or limited oversampling ratio and consequently lower achievable signal-to-quantization noise, or accepting a higher noise level due to inadequate settling of the analog operational amplifier components of the system.